First, a disclaimer: I knew Will very well back in the mid- to late-70s; we hung out together and went to many concerts. (A whole group of us were regular concert goers.) So my opinion of this book is certainly influenced by that personal connection.
In any case, Will looks at a somewhat arbitrary 5-year period in the 70s (he easily could have extended it a year or two in either direction), and goes into great detail about the NYC music scene during that time. Not only did it see the rise of groups from CBGBs and Max's Kansas City (Talking Heads, Ramones and others), the minimalists (Steve Reich, Philip Glass), performance artists, and the early days of hip-hop, but it also was a key time for the ascendancy of salsa, singer-songwriter rock (Springsteen, Patti Smith, etc.) and jazz. Will was always an eclectic listener, and among my friends, was the one with the most varied record collection. He writes here about all these styles of music - yes, even disco, which sucked - with erudition and feeling.
As I look back on the 70s from a distance, I realize that not only were those formative years for my own musical tastes, but that they did, indeed, have lasting influence. Will points out how much of this gestation was under the radar for years before becoming influential, and highlights a number of forgotten musicians and artists that were essential back in the day. (And there were plenty of non-NYC bands that passed through: the Grateful Dead, Pink Floyd, Emerson Lake & Palmer, Yes, Genesis - okay, I was a prog rock fan), Santana, the country rock bands like Lynard Skynard and the Marshall Tucker Band, and so much more.)
New York City in the late 70s was an amazing city for concerts. My friends and I would go to one or two a month, and many more in the summer (we'd hang out on the hill beside the Wollman skating rink in Central Park to listen to many of the concerts that we didn't care enough to pay for. Madison Square Garden, the Palladium, even the Nassau Coliseum were places we frequented, seeing shows by the big rock bands of the time, and in smaller venues, seeing an even broader range of performers. (And in spite of our lack of funds, these concerts were affordable.)
So there's a lot of nostalgia for me in the book. For others, who are younger, or not from NYC, you'll certainly learn a lot about the music scene, but especially understand how much of a connection there was among the different genres of the time. If you love music, read this book; you'll enjoy it.